Conventionally, this type of chiller apparatuses have a circuit configuration in which a refrigerant is circulated through a freezing cycle for cooling and a refrigerant cycle for heating within a pipe, and a work to be a temperature control target load is interposed and connected at a limited part of the refrigerant cycle. The freezing cycle serves as a primary temperature adjusting circuit with a circuit configuration in which: a refrigerant gas is compressed by an electric compressor and sent to a condenser on the discharge side as a high-pressure gas; in the condenser, the high-pressure gas is condensed and sent to an evaporator after going through an expansion valve of a decompression mechanism and being decompressed; and in the evaporator, the decompressed low-pressure refrigerant in a gas-liquid mixed state is evaporated and sucked into the intake side of the electric compressor so that the compression is repeated again. The refrigerant cycle serves as a secondary temperature adjusting circuit with a circuit configuration that: shares the evaporator of the freezing cycle; collects and stores a refrigerant liquid in a low-pressure liquid state in a refrigerant tank; and heats the refrigerant liquid in a heating apparatus (heater) mounted in the refrigerant tank as appropriate, or does not heat it but returns the refrigerant liquid suctioned, by a pump, from the refrigerant tank to the evaporator by interposing the work.
The rotational speed of the compressor provided to the freezing cycle and the heating temperature of the heating apparatus provided to the refrigerant cycle here are controlled by the control apparatus according to a temperature difference between the set temperature and the work temperature, the control apparatus being provided for selective temperature setting within a predetermined temperature range (for example, −20° C. to 60° C.) for use by a user. Temperature sensors are provided to the freezing cycle and the refrigerant cycle, respectively, and a work temperature is detected by a temperature sensor provided to a part on the side of the pump of the refrigerant cycle that is closer to the work. The work temperature here may be usually often close to an ambient temperature (for example, around about 20° C. to 25° C.) which is about the room temperature, but is not necessarily so. Therefore, the relationship between the work temperature and the ambient temperature does not matter here.
In the control apparatus, control in different operation modes is performed according to a temperature difference between an initial set temperature and a work temperature. For example, at a time of high temperature setting with a temperature difference resulting from the set temperature being far higher than the work temperature (for example, the temperature difference is 10° C. or larger), an operation mode of prioritizing a heating function is implemented such that, because a cooling function of the freezing cycle is unnecessary, the rotational speed of the compressor is suppressed to be low, and the heating temperature of the heating apparatus of the refrigerant cycle is set to be high so as to remove the temperature difference. Also, at a time of low temperature setting with a temperature difference resulting from the set temperature being far lower than the work temperature (for example, the temperature difference is 10° C. or larger), an operation mode of prioritizing a cooling function is implemented such that, because a heating function by the heating apparatus of the refrigerant cycle is unnecessary, heating setting of the heating apparatus is not performed, and the rotational speed of the electric compressor of the freezing cycle is set to be high so as to remove the temperature difference. Furthermore, at a time of temperature control setting with a small temperature difference resulting from the set temperature being close to the work temperature (for example, 5° C. to 10° C.) (including a case where the above-mentioned operation mode of prioritizing the heating function, and operation mode of prioritizing the cooling function are continuously implemented, and the temperature difference became small, and a case where there is no temperature difference initially), both the heating function by the heating apparatus and the cooling function of the freezing cycle are implemented, and specifically, an operation mode of switching between the heating function and the cooling function is implemented such that the rotational speed of the compressor is slightly increased or decreased from a predetermined value or heating by the heating apparatus is slightly increased or decreased from a predetermined value so as to remove the temperature difference.
Note that well-known techniques related to a temperature control function of such a chiller apparatus include, for example, a “chiller apparatus” that can operate stably over a wide temperature range and accurately control the temperature of a coolant (see Patent Literature 1), a “chiller apparatus” that does not require a large heater and can accurately control the temperature of a coolant (see Patent Literature 2), and the like.